The use of SFP+ modules for creating high speed duplex channels with up to 10 Gbps data rates is generally known (e.g., see http://en.wikipedia.org/wiki/Small_form-factor_pluggable_transceiver#cite_note-spec-11, SFF-8431). For example, wavelength division multiplexing (WDM) SFP+modules are generally intended for creating a duplex communication channel in a single fiber.
Disadvantages of this method are the low efficiency use of the fibers and the impossibility to simultaneously connect other devices to the same fibers.
The use of optical circulators for the transmission of two data streams in different directions via the same fiber and at the same wavelength is also generally known (e.g., see U.S. Pat. No. 5,212,586). An optical circulator is a fully passive device, the operation principle of which is based on the effect of nonreciprocal rotation of polarization planes (i.e., the so-called Faraday Effect). Two mutually orthogonal polarized planes are used for data transmission. One of them conducts the optical signal in one direction, and the other one, in the opposite direction.
Disadvantages of this method are the relatively high cost determined by the price of the optical circulators and the low efficient use of the fibers (e.g., this efficiency is limited by the transparency windows of the optical circulators).